1. Field of the Invention
The present invention relates to adjustable lenses for use in general photography, cinematography and videography and more particularly for such a lens with a self-illuminated scale.
2. Description of Prior Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
The present invention addresses the problem of the lack of visibility in low or nonexistent light conditions of the markings on a lens body that show the position of the iris, focus, zoom or other appropriate scales and markings. To provide images of sufficient quality, lenses have to be adjusted by the users to control focus settings, aperture adjustments, and (for the case of zoom lenses) focal length settings. To aid the user in the adjustment process, lenses are typically marked with a set of adjustable scales so that the user can adjust the settings by aligning scale marks situated on a movable part of the lens with fiducials on an adjacent stationary part of the lens. Our invention improves the visibility of lens markings and provides assistance for the user in aligning the scale markings with the fiducial marks.
Traditional approaches to making lens scales and markings more visible have been to use markings with special characteristics; these include oversize markings, the use of contrasting colors, and the use of luminescent materials (including fluorescent, phosphorescent, and radio luminescent paints). The last materials have been used in an attempt to improve visibility in low light level conditions. Occasionally the use of an external lamp has been employed to aid the photographer/cinematographer in clearly seeing the position of lens scales and markings.
However, the use of photoluminescent paints has the drawback that such paints continue to glow even when not needed and thus need to be shielded to prevent casting stray light that can adversely effect the image produced by the lens. Radioluminescent paints are no longer used because of the health hazards.
The use of external viewing lamps is contraindicated because they can block the markings from certain angles. Further, such lamps occupy critical space around the operators' working space and have to be powered externally.
Using bright color engravings on matte black backgrounds and large numerals improve the visibility of the markings somewhat. Additionally, it is advantageous to provide a window in the focus scale cover so that while the focus scale rotates on average 300 degrees, the window only permits viewing of the nearest 60 degrees of marks to draw attention to the correct portion of the focus scale. However, these approaches do not improve the situation sufficiently under many conditions.
Our invention is fundamentally different in that our lens self-illuminates its own scales and markings. It does this without allowing any significant amount of light to escape from the lens housing. Accordingly, the scales are illuminated without interfering in any way with the quality of the images being taken.
We are aware U.S. Pat. No. 4,183,661 issued Jan. 15, 1980 to Ohkura. That patent discloses a scale illuminating mechanism for an enlarger lens system. Thus, it relates to lenses of a different type than involved here. Further, that mechanism is intended only for illumination of the iris control.